Marine propulsion



Dec. 18, 1945. c. D. VAN'PATTEN 2,391,109

MARINE PROPULS ION I 2 Sheets-Sheet 1 Filed Aug. 20, 1941 INVENTOR BY didrleafl tghliwzfia Dec. 18, 1945. c. D. VAN PATTEN 2,3915109 MARINE PROPULSION Filed Aug. 20, 1941 2 Sheets-Sheet 2 I gig-T. I v IIN'VENTOR (Jar/ea 3 2514: afia BY 4 y Patented Dec. 18, 1945 i UNITED a STAT Es Bar-Em ome s Thisinvention'relates' to marine propulsion'and haslfor itsprincipal object the provision of a new and novel marine propulsion-device that is simpiein construction, iefllcient in operation and includes-certain marked advantages over conventional screwfltype propulsion devices.

Objects of the invention include the provision of'amarine propulsion device of particular advantageto shall-owdraft boats but in no sense limitedthreto; the provision of a marine propulsion device comprising a unit'securable as such to aboathull and including a horizontally disposed line of shafting arranged in approximately perpendicular relationship with respect to the longitudinal center line of the boat and carrying a plurality of disc-like elements each arranged with the general plane of thickness thereof at an angle to the axis of rotation thereof and to a planeperpendi-cular to such axis of rotation; the provision of a structure 'as-above described in which the unitincludes a housing forming a gear casing and includes a driving shaft arranged in approximately perpendicular relationship with respect 'to-the axisof the line of shafting carry ing the discs; and suitably geared thereto; the provision of a construction as above described in which theunit includes rudder means supported thereby; the provision of a construction as above described in which the housing is provided with a 1 cover plate for the gear chamber and the rudder means is carried by the cover plate; and the provision of a construction as above described in which therudder' means includes a plurality of rudders one positioned rearwardly of each of the disc-like elements. I 1

Other objects of the invention include the provision of a marine propulsion device comprising a disc-like element adapted for rotation about a horizontal line disposed approximately perpen (near-any with respect to the longitudinal axis of the boat and arranged with the general plane of the disc at an angle to its axis of rotation, those edges of the disc di-sposedmme remote from the point of intersection of the plane of the disc with its axis of "rotation being turned or warped in a directiontending toreduce the overall length of the disc'measured in the direction of its axis of rotation: the provision of a marine propulsion device as above d-escribed in which the'warping of the diametrically opposite sides of the disc occurs along a sine curve; and the provision of a construction as above described in which the amount of warping or bending of the diametricaliy opposite sides of. the discis such fasto bring a the edges of the disc at'the point of maximum warping or bending thereof approximately into planes perpendicular to the axis of rotation of the i c-f f v Further objects of. the. invention include .the provision of g n'larine, propulsion device including a pair of cooperating hubmembers between the v opposed faces of which a' disc is adapted to be clamped, such opposed faces of the two hub members being disposed at an angle to the axis of frotation thereof and to I aplane perpendicular thereto, whereby in service the 'angularity of, the disc may be changed by substituting a diiierent pair of hubmembers having different angularity between the opposed faces thereof; [and the provision of a construction as above described in which means are provided for positively locking the disc to atleast one of the hub members.

' A further object of the invention is "to provide a marine propulsion device in the form of a dis adapted. to rotate about a horizontal axis disposed in approximately perpendicular relationship with respect to the longitudinal center line 'ofthe accompanying boat and disposed with the plane of thickness thereof at an angle to the axis of'rotation and ma plane perpendicular thereto, the peripheral edges of the discbeing formedto pro vide saw-like teeth. f

Still another object of the present invention is the provision of a marine propulsion device in cluding a disc-like element arranged for rotation about a" horizontal line approximatelyperpendicular tothe longitudinal axis of the boat and arranged with the "general plane'of thickness thereof at an angle-to its axis of rotation and to a plan "perpendicular thereto, together with means r01 dynamical-1y balancing the disc; and the provision of a construction as above described in which balancing weights are associated withthe disc in oppositely ofise't relation with respect to each" centrallyoflset side thereoffthe mass and position of the weight being suchas to provide a dynamically balanced assembly. I

"still iurther ob jects of the present invention include the provision of a marine propulsion device including adisc-like element arranged for rotation about an'approximately horizontal line disposed in approximately"perpendicular rela-' tion'ship with respect to the longitudinal center line of the associated boat and disposed with the general plane of thickness thereof at an angle to its axis of rotation and to a plane perpendicular thereto, together with means for varying the an-' gularity of the plane of thickness of the disclike element with respect to 'its'axis of rotation during operation; andthe provision of a marine.

propulsion device including a horizontally disposed shaft arranged with its axis inapproximately perpendicular relationship with respect to the associated boat and a disc-like element centrally mounted on the shaft in angularly adjustable relation with respect to the axis of the shaft, together with means cooperating with the disc enabling the angularity thereof with respect to the axis of the shaft to be varied during operation.

The above being among the objects of the present invention, the same consists in certain novel features of construction and combinations of parts to be hereinafter described with reference to the accompanying drawings, and then claimed, having the above and other objects in view.

In the accompanying drawings which illustrate suitable embodiment of the present invention and in which like numerals refer to like parts" throughout the several different views,

Fig. l is a side elevational view of a boat provided with a marine propulsion device constructed in accordance with the present invention;

Fig. 2 is a rear elevational view of the boat and propulsion device illustrated in Fig. 1;

Fig. 3 is a fragmentary, enlarged, partially sectioned plan view. of the rear end portion of the boat shown in the preceding figures and illustrating the propulsion device in horizontal section taken on the line 3-3 of Fig. 2;

Fig. 4 is a slightly enlarged, fragmentary, partially sectioned view of the same propelling mechanism as illustrated in Fig. 3 but equipped with a modified form of rudder construction;

Fig 5 is a fragmentary partially sectioned view similar to a portion of the propulsion devices shown in Figs. 3 and 4 but illustrating theapplication of balancing Weights to one of .the driving discs;

Fig. 6 is a fragmentary partially sectioned view illustrating a slightly different form of disc structure from that shown in the preceding views;

Figs. 7 and 8 are views similar to Fig. 6 but illustrating still further modified forms of disc elements;

Fig. 9 is a partial face view of the disc shown in Fig. 8 taken looking in the direction of the arrows 99 in Fig. 8;

Fig. 10 is an enlarged sectional view taken axially through a modified form of disc construc. tion and particularly illustrating the connection between the disc and its hub; and,

Fig. 11 is a more or less diagrammatic" fragmentary view illustrating a modified form of construction in which the angularity of the disc with respect; to the drive shaft may be varied during operation.

The present invention has been devised in an attempt to provide a marine propulsion device which eliminates the shortcomings of conventional screw propellers. The increases of speed in virtually all classes of vessels in recent years have been accompanied by a corresponding decrease in the propulsive coefficient as the displacement: power ratio has improved and engine power has gone up. As is obviou to students of the art, this diminution of propeller efficiency is due to the inherent and inescapable limitations of the screw form of propeller. This is not to say that vast strides in screw propeller design have not been made in late years. Much effort has been expended and the results are considerable, especially in the metallurgical and manufacturing aspects, but the screw at prese t constitutes the principal limiting factor towards increase in vessel performance, economy and cruising radius. The substantial improvements in hull forms, structures and power plants of recent years have largely been inhibited by the limitations of the screw principle of propulsion and :the device of the present invention largely disposes of those limitations inherent in screw propellers that has thus limited the advance in performance of boats as above described.

In its simplest form the present invention consists of a disc-like element mounted at the stern of the boat and arranged for rotation about a substantially horizontal axis disposed perpendicular to the longitudinal center line of the boat or to the direction of desired thrust thereon, the disc-like element being arranged with the general plane thereof disposed at an angle to its axis of rotation as well as to a plane perpendicular to such axis of rotation. It is preferably arranged so that in operation less thanhalf of its diameter is immersed in the water. Thus in sim ple language it comprises a type of wobble plate arranged for rotation about a line perpendicular tothe longitudinal aXis of the boat and with the lower portion thereof immersed in the Water. As the disc rotates, the two sides of the disc alternately exert pressure upon the Water in varyin oblique directions the reaction to which is a directly opposite thrust. Since two or more opposed discs or plates are normally employed, the varying oblique pressures are resolved into a linear propulsive thrust component in the direction of rotation. The action of the disc is somewhat analogous to that of sculling with an oar and when two discs of opposed angularity are employed the lateral components between the discs and the water are balanced and the resultant component of thrust is directed longitudinally of the boat. While ordinarily, from the standpoint of simplicity in construction, both discs will be mounted upon a single shaft, it will be appreciated that in the broader aspects of the invention this is not necessary as each disc may be mounted upon its own shaft if the two shafts are connected together for equal rotation and in such case-the individual shafts may be disposed at anangle to each other either in' a vertical plane, a horizontal plane, or in both.

In accordance with one phase of the present invention these discs form a part of a unitary structure that is applicable to and removable from the stern, or other suitably located support on or of a boat, as such. This unit includes a casing or housing for the disc shaft or shafts which housing is formed for removable securement to the stern of a boat. The housing or casing also serves to rotatably support a drive shaft suitably interconnected, as by gears or the like, with the disc shaft or shafts for applying driving movement thereto. Where the boat is of the in-board engine type, then the power shaft is preferably arranged to project through the stern of the boat within the area of securement of the casin thereto and interiorly of the boat is suitably connected tothe engine. The device is adaptable to an outboard type of construction in which case the engine is mounted upon the housing or casing and the drive shaft suitably connected to the crankshaftof the engine.

The angularity of the disc with respect to its axis of rotation is somewhat analogous to the pitch of a propeller. For instance, a disc arranged in a plane perpendicular to its axis of rotation would be equivalent to a propeller vhaving a zero pitch, and as the angle of the plane of the disc increases with respectj-to a plane perpendicular to its axis 30f rotation it corresponds with increased pitch in a screw propeller. 7 Experiments conducted upto the time of filing this application manner, but it will be appreciated 'thatfur-ther experiments will undoubtedly indicate that discs arranged with their planes of thicknesses at greater or lesser angles than those stated may entirely satisfactory and practical.

ltwill' be appreciated, of course, that these discs are subject to various modifications both in size, shape; mounting and speed of rotation; as well as mother respects a number of which are disclosed hereinby way of explanation. I

.Itrwill, of course, be appreciatedthat in the employment of they present invention it is preferablei'that the depth of immersion. of the driving discs be approximately predetennmed during normal operation. For that, reason it is, preferable, although not necessary in all cases, that the presentinyention be employedwith boat hiulls of the transom stern type inasmuch as with such types of bulls at. any time speed in excess oflthat speedatwhich the watereddies or .burb1es3-up back, Ofjhe transom, and which for smaller boats at least may be in the approximate neighborhood of seven knots, the water will'break away from the stern in a, substantially smoothisurface reardless' of load, and thus predeterminethe depth ofjimmersion of the associated discs;v I o 7 Referring .now to the accompanying drawings and particularly. to Figs. .1, 2 and 3 a conventional V-bottom type of boat is shown generally at 2'0 and as having a sterntransom 22.. Asmdicated best in Fig. 2 the lower edge of the transsom '22is, straight and as previously explained this is a desirable characteristic of any boat to accordance with. the present. invention may be 7 mounted upcn the stem or other suitablepontion of a bcatwhere such portion is of sufficient width tofaccommodate them, but as .a matter of illustration the boat '20 shownis assumed to be arelfatively small boat with the transom-.22 of awidth suitable for accommodation of a single unit. lAccordingly, there is shown mounteduponthe transom 22 a propulsionunit including a housing jin dicated generally at H which forms a casing for the gear and bearing elements of the device as well as a support therefor. Where the invention is to be applied to an outboard engine type of con-- struction, then the engine may be mounted directly on and above the casing or housing .Hwith its crankshaft axis vertically disposed and suitablygeared to the disc shaft or shafts in any well known and conventional mannen 'When theinvention is applied to an inboard engine type of construction, then the engine of course, placed within the boat hull and is connected by a suit-' able drive. shaftprojecting through the'stern of the boat and intoithe housing where it issuitably geared to-the disc s-l'iait or shafts. This latter type of construction is shown by way of illustration and in accordance therewith an engine 24 which may be of any suitable or conventional type but which will usually be of a conventional internal. combustion type is suitably mounted within the boaithull with the axis of its crank: shaft preferably'extending, longitudinally of the hull and. centrally thereof as indicated The panticular casing or housing H shown .by way of illustration includes a forwardly extending, hollow portion the forward end of which is'provided an outwardly directed encircling flange 28 abutting the rear surface of the transom 22 and through which bolts 30 extend, and. cooperate with nuts :32 to provide a mounting for the unit on the transom '22. 1 If desired gaskets or othersuitable sealing means (not shown) may bei-interposed between the flanges 2 8 and the transom 2-2 to provide .a water-tight connection rtherebe tween. Rearwardly of the portion 126 the housing H is provided on each side thereof with'an outwardly extending hollow portion 34 of gradu ;ally reduced cross-sectional area centrally between and within which the driving disc shaft means is rcitatably supported. While such driving disc shaft means may be either a single shaft or a pair of shafts suitably connected together adjacent their. centers, for the purpose of illustration in the drawings a single shaft 36 is shown. The shaftIS'B is arranged with its axis horizontal and perpendicular to the longitudinal center line .of the boat '28 and is supported at the outer ends of the portions 34 by means of suitable bearings. here indicated as roller bearings 38. The shaft 36 projects outwardly beyond the ends of the portions 34 and is sealed against leakage to the hous ing portion '34 by means-of suitable or conventional shaft sealing elements 40. The central portion of the' haft 36 may be suitably supported for rotation in any desired manner but in the particular case shown by way of illustration is nonrotatably received within a hub-like carrier 42 for a ring gear 44 moun tedthereon for rotation-com centrically with the shaft 36. The carrier 42 itself is mounted for rotation in bearings 46 on each side of the "ring gear 44, the bearings 46 being each mounted in a suitable carrier 48 threadably rece'ived in a corresponding supporting wall 553 formed integrall with the housing H. o

The engine 24 may be connecwd to the gear 44 in any suitable manner but in the present case, and as a matter of illustration, a pinion shaft '52 is rotatably mounted in a bearing carrier 54 axially adjustably mounted within the for ward extension 26 of the housing H and at its rear end is provided with a pinion 56 integral therewith arranged in meshing relationship with respect to the-ring gear 44. The carrier 54 being adjustable axially of the pinion shaft 52 and, therefore, longitudinally of the boat, and the ring gear 54 being axially adjustable through adjustment of the carriers 48, proper meshing relationshipIo-f the ring vgear 44 and pinion 5B is provided for. The drivingratio established between the pinion 55 andring gear 44 may be any desired and will, of course, vary with the relative power output of the engine, diameter and normal depth of immersion of the driving discs, as well as with other factors, but for the purpose of illustration it may b assumed that in the particular em-' bodiment shown the pinion 56 will turn two to three times as fast as the ring gear 44.

As indicated in Fig. 3 the forward end of the pinion shaft 52- 'projects through the transom 22' within the area of the flange 28 and within the boat 20 is connected by a short shaft 60 and preferably a pair of universal joints 6'2 with the drive shaft for the engine 24. Thus operation of the engine 24 causes rotation of the pinion shaft 52 and pinion 56 and consequent rotation of the ring gear 44 and shaft 36. .The rear end of the housing H is provided with an opening 64 therein through which the ring gear 44 and its mounting parts may be introduced into and removed from the interior of the housingand through which access may be gained to the bearing carriers 48 for the purpose of adjusting the position of the ring gear 44 axially thereof.

The opening 64 is closed by a removable cover plate 68' suitably secured in position by means of cap screws 68. The cover plate 66 also forms a support for a rudder l and for this purpose the cover plate 66 is provided with brackets 12 adjacent its upper and lower edges to which the rudder To is pivotally connected by means of pins such as 14, the pins 14 being arranged, ofcourse, with their axes vertically disposed. The rudder 10 is provided with a laterally ofiset arm 16 the free end of which is connected by a'ball joint 18 with a link 8! the forward end of which is pivotally connected as at 82 on a verticalaxis with the rear end of a rod 84 which passes through the transom 22 and extends to any suitable type of, steering wheelor the like (not shown). Suitable packing such as 86 may be provided in surrounding relation with respect to the rod 84 to prevent leakage of water through'the stern of the boat around the rod 84.

The outer ends of the shaft 36 where they project outwardly beyond the corresponding ends of the housing H form the support for the angularly disposed discs which provide the propulsion means for the present invention. While one or more discs may be mounted on each end of the shaft 36, and where more than one is so mounted each outer end of the shaft may require additional support by an outboard bearing, for the purpose of illustration only one disc is shown mounted on each end of th shaft 36 and will usually be found suficient for most purposes. Accordingly, there is shown fixed to each outer end of the shaft 36 outwardly beyond the corresponding end of the housing H a disc 90. Each 1 disc 90 is provided with a hub 92 within which the corresponding end of the shaft 36 is nonrotatably received and it is secured in position thereon by means of a nut 94 threaded on the end of the shaft 36. with the general plane of thickness thereof at an angle to the axis of the shaft 36 as well as to a plane perpendicular to such axis. As previously mentioned experiments to date have indicated that satisfactory results are obtained where the angle of the plane of thickness of the disc is arranged between 35 and 45- with respect to a plane perpendicular to the axis of rotation, but it is presumed that further experiments will indicate that disc angles both above and below this value may be employed and may be preferable under some conditions of operation. The discs 90 are arranged in opposed relationship, that is that edge of one disc which extends closest to the center line of the boat is arranged in the same angular relationship with respect to the axis of the shaft 36 as the corresponding edge of the other disc 90. It will be noted that the discs 90 are of a diameter such that they project below the plane of the bottom of the boat adjacent the transom 22 an amount somewhat less than half of the diameter of the discs. This means that when the boat 26 is running at a normal speed the water leaving the stern of the boat will flow substantially horizontally therefrom and, there- Each disc 90 is arranged fore, predetermine the depth of immersion of the discs in'such water.

The discs 90 in Figs. 1 to 6, inclusive, are illustrated as having those marginal edge portions thereof spaced from each other axially of the axis of rotation by the greatest amount as being bent or curved out of the generalplane of the discs toward a position more nearly perpendicular to the axis of rotation, this being a preferred arrangement as will hereinafter be more specifically described. However, for the purpose of explaining the action of the discs 90 upon the water and how a propulsive thrust is obtained thereby, it is believed that it will be preferable for the moment to assume'that the discs 90 are flat as indicated in Fig. 7 and not curved or warped as shown in the preceding views. From an inspection of Fig. 7, it will be noted that the disc 90a there shown is identical to the disc 90 previously described except that it isperfectly fiat or coplanar, but is disposed with the plane of its thickness at the same angle with respect to the axis of rotation as the general plane of the disc 90 shown in the preceding views.

In operation the discs 90, when the boat is traveling in a forwardly direction, rotate in a direction to carry their upper edges forwardly and their lower edges rearwardly. The lower portions only of the discs being immersedin thewater during normal operation and in moving relatively rearwardly with respect to the boat alternately presents one surface and then the other surface thereof in an oblique position against the water thus tending to press the water in contact therewith both rearwardly and laterally with respect to the axis of rotation of the discs. The two discs being arranged in opposed relationship the lateral thrust components ofiset one another with the result that the resultant forceof the discs acting upon the water is exerted in the direction of the longitudinal center line of the associated boat hull. When a perfectly flat disc such as the disc 90a illustrated in Fig. 7 is employed, there is a definite maximum degree of immersion of the disc during normal running operation that should not be exceeded. This is because of the fact a negative thrust component is incurred where the relative depth of immersion and angle of the disc are such that the nominal or running load water lines of the disc intersect-at the fore and aftand perpendicular positions of the disc rotation since, in this situation, a portion of the immersed area of the disc moves relatively forward during the working part of the cycle. With a flat disc the maximum depth of immersion possible before incurring this negative thrust component is calculated according to the equation:

M K i/tan 0 where M=Depth of immersion as a fraction of diameter. 0=Angle of disc with plane of rotation. K=Coefiicient experimentally determined as .2125.

Besides producing a negative thrust where immersed too deeply as above pointed out the flat disc, such as illustrated in Fig. '7, has a source of loss which is present regardless of the depth of immersion that is occasioned by the downward and upward travel of the disc at an acute angle to the surface of the Water at the beginning and end of the cycle and the lifting of a quantity of water above the normal water line at the end of the working portion of thecycle, which concomitants of the action accomplish no useful work.

2,391,109 This lifting or the water at he end of the working cycle-issomewhat analogous to the lifting of the water by a non-feathering paddle wheel.

I The above described disadvantages of the completely flat disc, both from excessive depth of immersion during normal running conditions and the tendency to li-ft water above the normal sur face of the water at the end of each working cycle 'offthe' disc maybe substantially avoided by properly warping or bending the discs in the-manrier illustrated in Figs. 1 to 6, inclusive. This formation of the disc is obtained by warping or bending the outer tips of the disc towards the the discs" more nearly constantly vertical. Preferably the axially outertips of the disc are warped axially inwardly until the plane of the extreme margins of the bent portion approaches parallelism with the plane of rotation. The warping of the discserves a function somewhat analogous to the feathering of-the blades of' a paddle wheelbut without the necessity for-oscillation of the bladesandits attendant" problems and power absor'ption. The'most important function of the warped conformation is, of" course, the elimination of the opposing orneg'ative thrust components or retarding action inherent in a fiat disc having a 'd'iametcr-draft-angle function'outside of the critical limits previously-mentioned.

' It is, of course, true that the warped disc has warp'a'ge of disc curvature, the acceleration of pressure does not approach the proportions of impact. I

With awarped discneither the maximum nor the optimum depth of immersion appears'to be mathematically calculable since the degree and nature of warping can be so accomplished as to eliminatethi's negative thrust component at any practical disc tangent angle and at any depth of immersion up to 50% ofthe diameter. Rather, the maximum depth of immersion appears to be dependent on thesizeand'design of the gear housing which must obviously be above the bottom of the transom 22 of the boat 26 and which size-and design are in turn determined upon the gear size and design. At the present time it appears, bothfrom the standpoint of logic and fromexperimentations, that the optimum nature of warping consists of a simple bend in a sine curve of the outer portions of the tip of the disc toward,

the plane of rotation which curve extends from andis tangent to 'a'central fiat portion adjacent to the hub of the disc and is also tangent to-the pla'neoi rotation at the tips.

the lowest boat speeds where the transom is not clear of the stern eddies and'the disc iszalnlost' 1 ortotally submerged, the efficiency of the propulb1'e range, say seven miles-perhour, the greater share of the time. 7

The question also arises regard-11g constancy of immersion in a seaway'. In this respect it may besaid' that it has been entirely possible with only a slight alteration from normal hull form to maintain constancy of immersion at least equal and comparable to a conventional screw propelled vessel. In the case of lifting the disc element of the present invention clear of the waterand the resultant racing of the engine, the effects are far less serious and annoying than with a screw due to the lower rate of rotation and the absence of individual and separate blades. Further, cavitation and racing will continue intermittently for an appreciable time'afterre-immersion of a screw propeller while the disc of the present invention bites immediately upon reaching the water.

Comparisons in the performance of a boat equipped with a conventional type of screw propeller and with a propulsion device constructed in accordance with the present invention indicate increases in speed of the boat with the same engi-ne of as much as 20% by the use of the present invention. A. consideration of the inherent sources of loss in a screw propelled boatas compared to a boat propelled by mechanism constructed in accordance with the present invention is explanatoryof the reasons why such increased performance is possible;

The major sources of loss in the propulsion device of the present invention can be resolved into a practical particular or quantity which might be termed orbicular loss which is the sum of the losses due to the'downward, upward sideward movement and acceleration of water resulting from the obliquity of pressure application of the disc. This source-of loss possesses, in certain ways, ananalogy in the loss which is the torsional component or the pressure on-the aft faces of the blades of the screw propeller, the corollary of is the rotation of the thrust column.

- Surface or skin friction obviously exists in the operation of both the screw propeller andthe disc of the present invention but is a complete loss onlyin the case of the screw. A minor part of the skin friction in the disc of the present invention results in loss due to adhesion and consequent lifting of water at the end of the working portion of the cycle, while the greater part of this friction provides a positive thrust component.

A. head resistance w-ithout skin friction and rather comparable to the rolling resistance of a wheel results momentarily each time the disc of the presentinvention becomes parallel to the center line of the boat but, unless the section of ent invention. This source of loss is occasionally termed "pron-1e or edge loss and isthe loss due to that portion of the torsional resistance not resultantfrom the pressure on the aft faces of the blades nor from skin friction. It is the loss due'to the plain edgewise resistanceoi the blades to rotation in the water where no thrust load or skin friction are considered, the factors in which are the thickness and sectional shape of the blades, the diameter of v the propeller and the peripheral speed. I

' Therates at which these foregoing items of loss vary in thetwo types of propelling means, relative to the several dimensions, proportions, ratios, speeds and loadings, are the key to accurate comparison and judgment between the screw propeller and the disc of the present invention.

For practical purposes of consideration the item which is termed orbicular lossin the case of the disc of the present invention probably varies virtually in direct proportion to the required specific power absorption. The counterpart of this loss in the case of the screw propeller increases at a much more rapid rate with increase in the required specific power absorption since increases in power in relation to displacement and resistance necessitates increases of I pitch, diameter and/or peripheral speed, and as has been previously remarked, losses tend to go up at an even more accelerated rate with increases in these dimensions beyond certain well established practical proportions and limits.

Skin friction undoubtedly varies at the same rate in both the screw and disc of the present invention in relation to peripheral speed, but since the attendant loss in the case of the disc of the present invention is a considerably smaller proportion, it is obvious that the disc of the present invention possesses an advantage here especially in the higher speed ranges. Inasmuch as the screw only is subject to blade edge resistance or profile loss and since this item is very considerable and increases at an accelerated rate with increases in peripheral speed, sectional thickness and shape, and diameter, it is evident that here another point of advantage falls to the disc of the present invention.

Additional advantages of the present invention due to the elimination of all water immersed appendages, as for instance propeller shafts and struts, excepting only the steering appendages, and the elimination of the resultant reduction of the resistance of these appendages in passing through the water, are self-evident and need little comment. With improvements in the displacement: power ratio, the proportion of appendages in screw propeller driven craft has increased considerably in most cases. Appendage resistance in the faster classes of screw driven. vessels accounts for upward of of the total resistance, and in some cases much more, so that a most worth while not gain in vessel performance ishad on this score alone by the use of the present invention.

Also self -evident is the advantage of the present invention in permissible structural sections and resultant durability of the working elements since blade edge or profile loss does not exist in the operation of the disc of the present invention. Furthermore on this score is the fact that since shafts, hubs, etc., are nominally out of the water in the use of the present invention their size and design are not limited by consideration to resistance to passage through water.

From the foregoing consideration of the relative, losses in screw propeller propulsion devices as compared to the present invention, those skilled in the art will readily appreciate the advantages of the presentinvention as compared to screw propellers and the possibility of obtaining increased performance in vessels equipped with the present invention over those equipped with conventional screw propelling means.

. It might be noted at this point that during operation of a-boat provided with a propelling means constructed in accordance with the present invention, a small amount of water will adhere to the discs on emerging from the water and will be thrown off of the periphery thereof in the form of fine spray. To obviate therpossibility of any of such spray being carried inboard to the discomforture of the passengers it will usually be preferable to providea 'hood'or shield, such for instance as isindicated in Fig. 1 by dotted'lines at I00, secured to the hull of the boat in overlying relationship with-respect to-the discs 90. r

Steering of a boat propelled-in accordance with the present inventioncreates no problem where twin-.;opposed discs areemployed as shown. A single rudder'mounted centrally between the two discs as shown and explained in connection with Figs. 1, 2 and 3- has been found to give adequate steering in the medium and higher speed ranges. A preferred form of rudder arrangement which gives entirelysatisfactory control at all speeds and. astern is illustrated in Fig. 1.

Referring to Fig. 4 it will be noted that the construction there shown is identicalto that previously shownexcepting only the steering apparatus. Consequently, a description of the steering apparatus only will be sufiicient to completely disclose the structure there shown. In this construction it will be noted that the cover plate 66 is replaced by a similar ,cover plate 66' except that in this case the plate 66' is provided at each side thereof with a pair of vertically spaced rearward ly and outwardly projecting arms I02 the outer ends of which extend into substantial alignment, longitudinally of the boat, with the centers of the corresponding discs Between the arms I02 on each side of the .cover plate 66 a rudder element I04 is pivotally mounted upon a vertical axis I06. 7 The two rudders I04 at a point rearwardly of their corresponding pivot I06 are each pivotally connected as at I08 to the outer end of a corresponding cross-link I I0 the inner ends of which-are pivotally connected together as at II2 which thus constrains them to approximately equal pivotal movement. Pivotally mounted at I I4 about avertical axis and on a cross-arm IIB connecting the outer ends of the upper arms I02 is a bellcrank II8 one arm of which is pivotally connected to the inner ends of the links I I0 by the same pivot pin I I2 which interconnects such links. The other arm of the bellcrank I I8 is connected to a ball joint I8, corresponding to the ball joint la previously described and which is connected to a suitable steering wheel or the like within the hull .of the boat 1 Because of the obliquity of the discs 90 it will be appreciated by those skilled in the art that a condition of dynamic unbalance theoretically results due to the center of mass of the two opposite halves of each disc being spaced from each other axially of the axis of rotation. As a matter of fact this apparent unbalancehas proven to be of little practical importance primarily due to the fact that the thrust of the disc in the water offsets the forces arising from this unbalanced condition to a greater or lesser extent. However, where it is desired to eliminate this condition of unbalance resort may be had to a, construction such as illustrated in Fig. 5. The disc 90b in Fig, 5 may be considered identicalto the disc 90 previously described and as being provided with a hub 92b identical with the hub 92 of the disc 90. Projecting outwardl from the hub 92b on diametrically opposite sides thereof are a pair of arms I24 each terminating in a weight I26. The arms I24 preferably lie approximately in a plane disposed at the same angle to the plane ofrotation as the central portion of the disc 901) but on the opposite side thereof the plane of rotation passing centrally through the disc 90b. The arms I24 and weights I26 are of a suflicient mass to dynamically balance the corresponding half of the disc 90b with respect to the central plane of rotation between them under rotating conditions,

The construction, therefore ei fects the dynamic balance of the assembly; ,The arms I24 are, of

course, prefierably of such length that the weights I16 will'not become immersed in. the water during rotationof the discunder normal running conditions.

inth-e direction of obliquity of the discfEIIle and preferably with. aplurality of. smaller openings It; willyof course, appreciated that because tack bysuch vessels by laying metallic cables.

orr'nets'over or close to the surface of the water t be protected. Under such circumstances if a conventional screw propellerpropelled type of boat'attempts to-enter such water the cables or nets: become fouled in the propeller and thus render-the boat uselessand vulnerable to attack. By theusei oi the disc propelling. means of the presemt invention such boats are enabled to pass over such'eablesor nets with no d-iiilcultyat all 'and' may even be aided-in such case particularly if such cables or nets are sufiiciently anchored to provide asubstantialsurfaoe againstfwhich the thrustoi the discs-maybe exerted.

in fact the present invention particularly lends itself to modification to facilitate the destruc tion of. the cables or nets above referred toand the manner of accomplishing. this is illustrated in- Figs. 8 and 9. Although in this connectioneither the straight or the warped discs may be em-ployedfthe disc 90c illustrated in Figs. 8 and 9 is shown as a perfectly flat disc for the purpose. of illustration. Its peripheral surface is.

formed. to provide 'a plurality of relatively small:

cutting teeth I30. In this case the. disc 900, or at'least the peripheral portion thereof, is preferably formed. from a material equivalent to that touridi in certain types of cutting tools. Obviously should a boat equippedwith driving discs such as the disc so'c shown. inFi'gs. 8 and? 9 come inv contact wtih a metal. cable or net and could be maneuvered to bring the disc 900 into any degree of sustained contact with such. cables or nets the strands thereof will be quickly severed by'tlie cutting action of the teeth I'3Ilthereon when the disc is rotating.

In the constructions thus far described the discs-91f in eachca'se have been illustrated as beingprovi'ded' with an integral hub structure or" at least one that is permanently fixedwi'threspectthereto Under such conditions if it is desired'to replace a disc such as 90 withone'having ate this case is made up without a "hub but. witiia central opening I4'2' preferably elongated I44. arranged. insa circle concentric with the center of the disc 99c and angularly spaced from. one another about such circle- The hub inthis case is made up; of. apair of parts M6 each having a central. splined'; bore: for reception on the portion. I40 of the: shafit 35 and opposed axially directed faces I48 arranged at an obliquity with. respect to the plane of rotation corresponding with that desired .for the disc 90c; One of the hub members I46 may be provided with a plurality of pins IEB secured therein and arranged; in a circle and; angularly spa-cedxfrom one-another correspondingv to the openings. I44 so as to be receivable in the openings I 44 and thereby positively lock the disc 90c against relative rotation' with respect thereto. The disc 90c is interposed between the faces M8 of the hub mem;

bers- I46 with the pins tEIlwreceived in the openings I 44 and thenut fle inbeing drawn up firmly clamps the disc 99c between the-hub members I46. and fixes it at the desired angle: with respect to the plane of rotation. With this construction. various .sets of hub; members I 46 may be provided withvarying angularitiesof thexfaces- H8 thereof so that in event it is desired to change: the angle of a disc all that is required is a. pair of hub members I 46 having cooperating faces I48 of the required angularity. Under'suchi circumstances the disc member 90c and hubmembers I46 are removed from the shaft 3&upon: removal of the nut 94c, upon which the newset of hub members with the disc 906 between themv may be replaced on the shaft: 36,-th'e nut 94c replaced, and the structure isthen ready for operation'. Thehub'members I46 beingrelatively economical to manufacture permits the angularity of a disc such as We to be changed at a minimum of cost.

It may be founddeslrable under some circum-' stances to be able to vary the angularity of the driving discs duringoperation and under such circumstances a construction such as disclosed.

in Fig. 11, or it equivalent, may be resortedv to; Referringto.Fig..11 which illustrates one endonly of the drive shaft and a single disc associated therewith, it will. be understood. that the shaft 36" corresponds with the shaft 33 previously described and may be supported. and carried in thesame or a similar manner. On. the outer end of the shaft 36? a disc 90f. is mounted. The disc 9'llffis provided wit'ha fixed hub- 92 through which the shaft-J36" projects. .Apin ISO-projects throughthe hub 92? and diametrically throughthe shaft 36" and the bore of the hub 92f is elongated ina direction transverse to its axis and in a direction perpendicular to the axis of the pin I60 so that the disc il'f'may'swing about the axis of'the pin I60 which, of course, restraihs the disc 96'; to equal rotation with the shaft 38. Axially inwardly of the disc 90]? a ring-like member IE2 is mounted on the shaft 3'6 for movement axially thereof but is maintained against relative rotation thereon by means of one or more keys. I54.- The member IIiZ' is provided with. an outwardly projecting ear I66 thereon to which one endiof' a link I68 is pivotall'y connected as at I10. The opposite end of the link. IE8 is pivotally connected to an ear I12 formed on. the disc 90) as at I14.- Thus the position of the member. I62 axiallyof the shaft 36" determines the angularity of the: plane of thickness ofTthe disc 90) with respect-to the plane of rotation of the disc. In. order to c'ontrolfthe position ofthe' member I 62 onthe shaft 36', the member l62'is provided with ape ripheral groove I76. Pivotally supported as at l 18, on the housing H or otherwise, is a lever [80 having a yoke end I82 slidably engaged in the groove I16 at diametrically opposite points thereof. The upper end of the lever I80 may be pivotally connected by any suitable means suchas a link I84 with any suitable type or form of con trol member operation of which causes'pivotal movement of the lever I80 about its pivot point I18. As will be readily appreciated by the construction described the angularity of the disc =90 may be adjusted during its rotation so that any desired augularity thereof, within reasonable limits, may be obtained during operation of the propulsion device. 7

Formal changes may be made in the specifi embodiments of the invention described without departing from the spirit or substance of the broad invention, the scope of which is commensurate with the appended claims.

What is claimed is:

1. In a boat of the class wherein the hull terminates at its rear end in a transom, the combination with said transom of a propulsion unit mounted thereon and comprising a housing fixed to said transom, shaft means rotatalbly supported in said housing with the axis of rotation thereof disposed generally horizontally and transversely to the longitudinal center line of the boat, a drive shaft rotatably mounted within said housing, gearing connecting said drive shaft and said shaft means for simultaneous rotation, said shaft means projecting outwardly beyond said housing at opposite sides thereof, and a water displacement element comprising a disc-like member shaft means and to a plane perpendicular thereto,

said disc-like members being of such a size as to project below the lower edge of said transom.

2. In a boat of the class wherein the bottom is provided with a sharp rear edge from which the water flows substantially horizontally rearwardly during normal operation, the combination with said stern of a propulsion unit mounted thereon comprising a housing, a shaft rotatably mounted in said housing about a substantially horizontal axis extending perpendicular to the longitudinal center line of said boat and projecting beyond both sides of said housing, a drive shaft rotatably mounted in said housing in transverse relation.- ship with respect to the'first mentioned shaft, gearing connecting said drive shaft and the first mentioned shaft, said housing terminating at its bottom above the general plane of the lower edge of the stern of said boat, and a propulsion element fixed to each projecting end of said first mentioned shaft, said propulsion elements each comprsing a disc-like member fixed for equal rotation with said first mentioned shaft and arranged with the general plane of thicknessthereof at an angle to the axis of rotation of said first mentioned shaft and to a plane perpendicular thereto, said disc-like members projecting below said lower edge of said stern.

3. In' combination with a boat having a transom, propulsion mechanism comprising, a rigid housing having a longitudinal centerline in substantial parallelism with the longitudinal centerline of said boat, a horizontally disposed shaft rotatably mounted in said housing disposed transversely to the longitudinal centerline thereof and projecting beyond opposite sides thereof, a.

disc-like water engaging element secured to said shaft on each side of said housing each with the plane-of its thickness disposed at an acute angle to a plane perpendicular to the axis of said shaft, a second generally horizontally extending shaft rotatably mounted in said housing in perpendicular relationship with respect to the first-mentioned shaft, gearing within said housing opera- I tively interconnecting said shafts, and said housing being provided with a vertically directed surface arranged for securement to a complementarily disposed surface on said transom of said boat, said surface forming the sole area of contact between said mechanism and said hull.

4. In combination with a boat having a transom, propulsion mechanism comprising, a housing having a central portion, a horizontally and laterally directed tubular extension project-ing from each of its laterally opposite sides, and an additional tubular extension projecting forwardly therefrom in approximately the same plane as the first-mentioned extensions, the last-mentioned extension terminating in a vertically directed attaching and supporting surface adapted for rigid securement to the transom of said boat, a horizontally directed transverse shaft in said housing rotatably supported in the first-mentioned extensions and projecting outwardly therebeyond, a second shaft rotatably supported in the last-mentioned extension, gearing within said housing operatively connecting said shafts for inter-related movements, and a pair of disc-like propulsion elements of substantially unbroken circular conformation, each secured to a corresponding end of the first-mentioned shaft exteriorly of said housing, and each arranged with its axis at an acute angle to the axis of said first-mentioned shaft.

5. A marine propeller comprising a generally circular disc-like element adapted to be mounted for rotation about a horizontal axis disposed transversely to the direction of movement, said element having its general plane of thickness arranged in non-perpendicular relationship with said axis, radially oppositely-disposed, axiallyspaced segments thereof bein warped toward tangency with a plane perpendicular to said axis.

6. A 'marine propulsion device comprising a plurality of disc-like elements of generally circular form mounted for rotation about a horizontal axis, said axis being disposed transversely to the normal direction of movement, the general planes of thickness of said respective elements being disposed non-perpendioular with respect to said axis, and said elements having axially-spaced, oppositely-disposed segments thereof Warped toward tangency with planes perpendicular to said axis.

7. A marine propulsion device comprising a pair of generally circular disc-like elements mounted for rotation about a horizontal axis a which axis is disposed transversely to the normal direction of travel, the respective planes of thickness of said elements being disposed in equal and opposite non-perpendicular relationship with said.

- being constructed and arranged with its general plane of thickness in non-perpendicular relationship with said axis and having radially-oppo sitely disposed, axially-spaced segments thereof warped toward tangency with planes perpendicular to said axis.

9. In combination with a, boat having a transom, a propeller mounted abaft of said transom comprising a generally circular disc-like element; means mounting said element for rotation about a horizontal axis disposed transversely to the normal direction of boat movement and for partial immersion only in the water supporting said boat during normal operation, said element having its general plane of thickness disposed in non-perpendicular relationship with said axis and being constructed and arranged such that the immersed fraction "of the diameter thereof measured in a direction perpendicular to the surface of said water is equal to K /tan 0 where 0 is the angle of said disc with the plane of rotation and K is equal to .2125.

10. The combination according to claim 8 wherein a pair .of complementary arranged elements are used.

11. Th combination according to claim 9 wherein a pair of elements in complementarily opposed relation are mounted on a common axis of rotation and in spaced relation to each other longitudinally of said axis.

12. A marine propeller comprising a generally circular disc-like element adapted to be mounted for rotation about a horizontal axis disposed transversely to the direction of movement, said element having its general plane of thickness arranged in non-perpendicular relationship with said axis, radially oppositely-disposed axiallyspaced segments thereof being displaced from said plane of thickness such that at normal running immersion positive thrust is exerted throughout the entire immersed area of said element.

13. A marine propeller comprising a generally circular disc-like element adapted to be mounted for rotation about a horizontal axis disposed transversely to the direction of movement, said element having its general plane of thickness arranged in non-perpendicular relationship with said axis, radially oppositely-disposed, axiallyspaced segments thereof being curved sinusoidally into tangency with planes perpendicular to said axis.

14. A marine propeller comprising a generally circular disc-like element adapted to be mounted for rotation about a horizontal axis disposed transversely to the direction of movement, said element having its general plane of thickness arranged in non-perpendicular relationship with said axis radially oppositely-disposed, axiallyspaced segments thereof being curved into tan-gency with planes parallel to the plane of 30 rotation. 

